Pull-type harvesting implements utilize a draft tongue to connect the implement to the hitch of a tractor. The tongue is pivotally supported from the frame of the implement to permit the tongue to pivotally move relative thereto so that the implement can move from a transport position directly behind the tractor to an operative position behind the tractor, but offset to the side thereof.
The draft tongue also supports a drive line connectable to the power-takeoff shaft of the tractor to deliver rotational power to the operative components of the harvesting implement, such as the cutting mechanism and other crop harvesting apparatus supported from the frame of the implement. The drive line typically incorporates several universal joints to permit bends in the drive line to accommodate the pivotal movement of the tongue as the implement is moved between the transport and operative positions.
Typically, the frame of the harvesting implement will be made mobile through a pair of transverse wheels. When the harvesting implement is operated in the operative position and offset outboard of the tractor, it will often be necessary to change the direction of travel of the implement, which is accomplished through the turning of the tractor. If an imaginary line is extended from the rear axle of the tractor to a line corresponding to the axle of the implement interconnecting the transverse wheels, a point of intersection is obtained. The closer the point of intersection is to one of the implement wheels, the tighter the implement will be turned.
Several tongue and hitch designs have been provided to provide tighter turning characteristics. One such design is commonly referred to as the equal angle hitch mechanism in which the pivot point between the draft tongue and the tractor is located midway between the first two universal joints of the drive line so that any turns result in equal turning or deflection angles in the first two universal joints.
Another design is commonly referred to as the swivel hitch design as represented in U.S. Pat. No. 5,099,937. In this design, the turning movement is pivoted through a gearbox to eliminate the angular deflections in the drive line universal joints. While this swivel hitch design allowed a greater turning movement of the tractor relative to the draft tongue, and as a result moved the point of intersection of the line of the tractor axle with the line of the implement axle closer to the left implement wheel, further improvement is still available.
John Deere Company developed a bent implement tongue design to improve the turning characteristics of the implement, as is represented in U.S. Pat. No. 5,018,345. While this draft tongue design improves the implement turns, the tongue requires a bumper on the side of the tongue to prevent damage due to interference with the tractor tire.
It would be desirable to provide an implement tongue design that would be aesthetically pleasing, while improving implement turning characteristics.
Disc cutterbars have been utilized in agricultural harvesting implements for many years. Each disc cutterbar includes a plurality of transversely spaced disc cutters driven for rotation about a generally vertical axis. Each disc cutter has two or three knives pivotally mounted on the periphery thereof to sever standing crop from the ground through an impact action. For background information on the structure and operation of disc cutterbars, reference is made to U.S. Pat. No. 4,815,262, issued to E. E. Koch and F. F. Voler, the descriptive portions thereof being incorporated herein by reference.
The construction of disc cutterbars has evolved over the years to the configuration of having a modular construction with cutter modules and spacer modules, such as shown in U.S. Pat. No. 4,840,019, issued to L. J. Pingry, the descriptive portions of which are incorporated herein by reference. In some instances, the cutter modules and the spacer modules were integrally formed into one unit such as shown and described in U.S. Pat. No. 4,947,629, issued to R. Ermacora and H. Neuerburg.
It has been found that the specific use of the disc cutterbar apparatus, e.g. whether used as part of a disc mower, such as shown and depicted in U.S. Pat. No. 4,955,187, issued to C. van der Lely, which is typically supported at one end, or as part of a disc mower-conditioner which usually provides support to the cutterbar at both opposing ends thereof, carries with that use a different set of design parameters than other machines in which the cutterbar is utilized.
On a disc mower-conditioner drive shaft, the secondary power-takeoff drive shaft is typically supported in a cantilevered manner off of the front of the splined input shaft of the main bevel gearbox. Included on the secondary drive shaft is a constant velocity universal joint assembly and a slip clutch, both of which are quite heavy. The power-takeoff shaft is retained on the input shaft by a split clamp hub design.
As the power-takeoff shaft turns at high speeds, the centrifugal forces resulting from the unbalanced shaft/universal joint/clutch assembly are carried by the input shaft spline teeth and clamp joint. The secondary couple from the universal joints in the constant velocity joint are also imposed on the input shaft. The spline fit with the clutch hub is loose intentionally so that the assembly can be installed over the splined shaft.
This looseness of the external and internal spline teeth permits the assembly to be positioned off-center to the shaft. The centrifugal forces from the off-center mass and the forces of the secondary couple cause the assembly to whirl about the shaft centerline. The motion of the inner and outer splined parts wears the spline teeth causing more spline tooth clearance and increased relative motion, eccentricity and force as the machine is used.
The clamped split hub retains the splined hub to the splined shaft adjacent to the clamp, but not away from the clamp area. The reaction from the secondary couple is carried partly by the clamped hub portion which causes relative motion between the clamped mating surfaces in the clamp area. The spline teeth in the clamp area are, therefore, subjected to the same wear problem.
The centrifugal forces from the eccentric constant velocity universal joint/clutch assembly and from the secondary universal joint couple are supported by the bevel gearbox input shaft. The alternating forces can cause the input shaft to fail in fatigue resulting in the shaft to have to be made larger and/or be heat treated to withstand the forces. The support of the bevel gearbox also carries the vibrating forces and is, therefore, prone to failure as well.
Several alternative design solutions have been proposed to resolve the fixation problem of the clutch hub on the shaft, including an axially placed bolt that screws into the end of the input shaft to clamp the clutch hub against the end of the input shaft and rigidly fix the clutch for better support thereof, but did not adequately resolve the problem as these designs became loose over time. A further disadvantage was recognized in that the alternative designs did not include an alignment feature to position the drive shaft/constant velocity joint/clutch assembly concentrically about the shaft centerline.